Fatigue rate evaluation of a transparent polyester resin subjected to low-temperature environments

In structural applications, catastrophic failure caused by fatigue occurs with more frequency because usually polymers are chosen when reduction in weight is necessary and overload is applied on it. In this study fatigue, crack growth at a humid, and very low temperature in a transparent unsaturated polyester resin has been investigated. The tests were conducted at a constant applied load ratio R = 0.1 using two different crack to width ratios (a/W) of 0.2 and 0.35 at room temperature and −60 °C. Polyester resin specimens are fabricated. The test used for the experiments is ASTM Standard D647 under tension–tension loading. The experimental results have been expressed in terms of Paris Law parameters. The fatigue crack results show that the fatigue resistance increases with decreasing a/w. It also shows that it increases with decreasing temperature up to −60 °C as the material becomes stiffer at the extremely low temperature and the polymer matric particles were much less mobile and ductile and discovered that low temperature has a positive influence on the strength of composites. The dominant failure mode was a polymer matrix -tear failure that was driven by a crack in the x-direction starts with the pre-crack in the case of a/w = 0.35 and it was slow enough in a/w = 0.2 because of the high energy of bonding and networking through the polymer matrix. The results proved that there is no through-the-thickness crack propagation due to fatigue in the polyester matrix.